The conventional blade-type pump generally comprises a stator, a rotor and at least one blade, wherein the stator has a room defined therein. The stator has an inlet and an outlet so that the room communicates with outside of the stator. Fluid enters into the room via the inlet and leaves the room via the outlet. The rotor is eccentrically located in the room and the outer periphery of the rotor is in contact with the inner periphery of the room. Multiple blades are taken as an example. The rotor has slots for accommodating the blades therein. The blades each have one end pointing the center of the rotor and the other end of each of the blades is in contact with the inner periphery of the room. A space is defined between the inner periphery of the room and the outer periphery of the rotor. By the contact between the rotor, the blades and the inner periphery of the room, multiple partitions are defined to receive fluid.
When the rotor rotates back and forth, the blades are driven by the rotor and movable back and forth within the slots due to the movement of the rotor. The volumes of the partitions vary due to the back-and-forth movement of the blades, so that the fluid is sucked into the room via the inlet and leaved from the room via the outlet.
The centrifugal force generated from the blades due to the rotation of the rotor drives the blades outward so as to contact the distal ends of the blades with the inner periphery of the room to pump the fluid. However, when the viscosity of the fluid is high, there will be a gap between the distal ends and the inner periphery of the room and the transmission efficiency of the fluid is reduced.
U.S. Pat. No. 4,212,603, U.S. Pat. No. 5,087,183, U.S. Pat. No. 5,160,252, U.S. Pat. No. 5,181,843 and U.S. Pat. No. 5,558,511 respectively discloses a fluid transmission device which comprises a stator with an annular groove which shares a common center with the room. The axles of the blades are engaged with the annular groove which guides the movement of the blades. The rotor is eccentrically located in the room and the axis of each of the blades points the center of the rotor, so that the shape of the inner periphery of the room is like oval inner periphery which is difficult to be machined during manufacturing processes. Furthermore, the blades each have a certain thickness, in order to prevent interference between two adjacent distal ends of the blades and the inner periphery of the room, the distal end of each blade is made to be sharpened. The sharp distal end of the blade may vibrate when the fluid passes therethrough and noise is therefore generated. The vibration also generates partial thermo stress which accelerates fatigue of the material at the distal end of the blade.
The present invention intends to provide a fluid transmission device which improves the shortcomings of the conventional fluid transmission devices.